Prognosis in clinical cancer is an area of great concern and interest. It is important to know the aggressiveness of the malignant cells and the likelihood of tumor recurrence or spread in order to plan the most effective therapy. Prostate cancer, for example, is managed by several alternative strategies. One of every 10 men currently develops prostate cancer at some point in his life. In some cases local-regional therapy is utilized, consisting of surgery or radiation, while in other cases systemic therapy is instituted, such as chemotherapy or hormonal therapy. In addition, “watchful waiting” is a treatment option for elderly patients or those in poor health. In addition, “watchful waiting” is a treatment option for men with early stage cancer, or for elderly patients, since untreated prostate cancer may take years to reach a problematic stage.
Current treatment decisions for individual prostate cancer patients are frequently based on the stage of disease at diagnosis and the overall health or age of the patient. It has been reported that DNA ploidy can aid in predicting the course of disease in patients with advanced disease (stage C and D1) (Lee et al., Journal of Urology 140:769-774 (1988)). In addition, the pretreatment level of the prostate specific antigen (PSA) has been used to estimate the risk of relapse after surgery and other types of treatment (Pisansky et al., Cancer 79:337-344 (1997)). However, a substantial proportion of patients with elevated or rising PSA levels after surgery remain clinically free of symptoms for extended periods of time (Frazier et al., Journal of Urology 149:516-518 (1993)). Therefore, even with these additional factors, practitioners are still unable to accurately predict the course of disease for all prostate cancer patients. The inability to differentiate tumors that will progress from those that will remain quiescent has created a dilemma for treatment decisions. There is clearly a need to identify new markers in order to separate patients with good prognosis who may not require further therapy from those more likely to relapse who might benefit from more intensive treatments.
Several side effects of radical prostatectomy (surgical removal of the prostate gland), radiation therapy and hormonal therapy have been documented. The side effects of surgery include discomfort with urination, urinary urgency, impotence, and the morbidity associated with general anesthesia and a major surgical procedure. Common complications associated with external-beam radiation therapy include impotence, discomfort with urination, urinary urgency, and diarrhea. The side effects of anti-androgen hormone therapy can include loss of libido, the development of breast tissue, and osteoporosis. Given the complications associated with some prostate cancer therapies, a marker that could distinguish between tumors that require aggressive treatments and those that require conservative treatment could result in higher survival rates and greater quality of life for prostate cancer patients. Thus, a need exists for a biomarker that can determine prostate cancer patient prognosis. The present invention satisfies this need and provides related advantages as well.